1. Field of the Invention
This invention relates to a receiver that has a non-electronic gain control and, more particularly, a receiver that comprises a combination of elements that pass, attenuate, and detect a radiated electromagnetic signal.
2. Description of the Related Art
A conventional communications system generally includes, among other elements, a transmitter, receiver, and amplifier. If the transmitted signal is encoded, the amplifier output goes to a decoder, and, ideally, that output should be constant. Thus if the signal to the receiver becomes weaker, the amplifier gain must be correspondingly increased. Electronic circuits to provide automatic gain control are well known; however, tradeoffs are necessary among parameters such as bandwidth, cost, sensitivity, etc.
Systems operated by radiated signals are known for many remote control operations, including garage door openers, TV controls, etc. To the extent necessary, these systems rely on electronic gain control to provide the required dynamic range.
Ceiling-mountable infrared detectors have been disclosed for use in intrusion detection systems. Takahashi (U.S. Pat. No. 4,514,630) and Guscott (U.S. Pat. No. 4,514,631) have disclosed infrared detectors that use mirrors to define a field of view.